The present invention relates generally to cutting tools and cutting inserts and, more particularly, to indexable cutting inserts and cutting tools that use them.
For applications such as milling metal, replaceable cutting inserts reduce the time needed to fix broken cutting edges on a tool. Indexable cutting inserts permit the same cutting insert to be “indexed” to expose a plurality of different cutting edges so that, after one edge is worn or broken, another edge can be used without the need to get a new insert. It is desirable to provide cutting inserts that are indexable a large number of times to extend the working life of the insert. Because the insert must be securely supported relative to a toolholder to which it is mounted, usually along three supporting surfaces of a multiple surface insert and with a clamp such as a bolt, a substantial amount of the surface area of the insert must be dedicated to supporting the insert, often limiting the number of ways that the insert can be indexed. For certain machining applications, small cutting inserts are required, or small toolholders must be used which require small cutting inserts. In such applications, it can be difficult to provide an insert that is indexable to multiple positions because of the limited amount of surface area available on the insert. It can also be difficult to provide adequate reinforcement for the cutting edges of such inserts because the configurations used for reinforcing the cutting edges use up substantial surface area of the insert. US 2007/0071561, WO 2008/002204 and JP2010089250, all disclose cutting inserts comprising clearance surfaces of substantially constant width. U.S. Pat. No. 3,981,057 discloses a cutting insert comprising three primary cutting edges.
It is desirable to provide an indexable insert configuration that facilitates provision of multiple cutting edges on an insert having little surface area. It is also desirable to provide an indexable cutting insert wherein cutting edges of the insert are provided with substantial reinforcement in a manner that minimizes the use of insert surface area.
In accordance with an aspect of the present invention, a cutting insert is provided comprising at least three cutting edges, each cutting edge including a primary cutting edge, characterized in that each primary cutting edge is associated with a respective different side surface of the cutting insert, each side surface having a respective rake surface.